A branch of the Heritage Foundation plays David against the Gang of Eight’s Goliath.

The Corker-Hoeven amendment to the Senate Gang of Eight immigration bill was introduced on Friday, June 21, at about 3:30 p.m. But its authors hadn’t finished writing it; until 5 p.m., people were handwriting extra changes to the legislation on the floor of the Senate. Members didn’t receive the amendment in their inboxes until Saturday. And the fourth floor of the Heritage Foundation went on virtual lockdown.

Most of the big conservative think tanks in D.C. either support the Gang of Eight proposal or decline to take an official stance on it. If you don’t count smaller shops that are specifically dedicated to the immigration issue, Heritage Action is basically it. The lobbying arm of the think tank is only a few years old, but it aims to have an outsize influence on policymaking. And the Senate bill might be its biggest chance yet.

Heritage Action, which was formerly located in a townhouse on Capitol Hill, is now based on the fourth floor of the Heritage Foundation’s Massachusetts Avenue headquarters. And when Corker-Hoeven came out, it was buzzing until midnight. The group is all-in against the legislation, and cautiously expects a win. It wouldn’t be its first.

When the farm bill died in the House last week, there was much weeping and gnashing of teeth around the Hill — and plenty of criticism for Speaker of the House John Boehner. But Heritage Action was thrilled. The group held that the food-stamp cuts weren’t big enough — food-stamp spending has grown from $40 billion to $80 billion in four years, while the bill made only a 20 percent cut — and that the legislation was therefore unpalatable for conservatives. They put significant lobbying efforts into stopping the bill, and they ran critical radio ads in the districts of seven Republican members of the Agriculture Committee who voted to send the bill to the floor. They considered its defeat a big victory and hope the immigration proposal will go the way of the farm bill.

Heritage Action owes its existence in part to Obamacare. During the debate over the president’s health-care reform, representatives of the Heritage Foundation felt their hands were tied by their 501(c)(3) status. Lobbyists simply had more tools and, as a result, were often more influential. So the conservative giant decided to branch out and start Heritage Action. Think of it as the Heritage Foundation with teeth.

“Before — three, four years ago — we would have been reluctant to do that,” says Tripp Baird, the group’s senior legislative strategist, of its tussling with Republicans over the farm bill. “We would have said, ‘Well, they’ve done some good things here, we don’t like it that much, but all in all it’s a good bill.’ But if it’s got gimmicks that we’ve been blasting the left and center on for years, and Republicans are using the same kind of gimmicks, we’ve got to say something, and we’ve got to say it hard.”

“Saying it hard” is the trick. But Heritage Action has one significant advantage over the other right-wing firms and special-interest groups: access to Heritage Foundation members. There are about 1,000 in every congressional district, and they’re often well organized and highly motivated. An oft-repeated criticism in the wake of November 2012 was that the Right doesn’t know how to organize; the Heritage Foundation does. That makes for a stronger lobbying operation, since it’s easier to organize targeted phone calls. The organization also stays in touch with conservative community leaders and business owners who might have extra sway over their representatives. And each district has a sentinel who volunteers to organize grassroots efforts. On top of that, local leaders often report back to Heritage Action on what their congressional representatives say in private. It all helps the group keep detailed tabs on who is leaning which way. This structure gives it more clout in the House than in the Senate. It’s a level of influence that seems to have played a significant role in taking down the farm bill, and the group’s leaders think it has a good shot at preventing Gang of Eight–style comprehensive immigration reform in the House, leadership be damned.

That’s not to say that Heritage Action isn’t a Senate player, too, though. Dan Holler, the group’s spokesman, says that after Senator John Cornyn (R., Texas) introduced a border-security amendment that Heritage Action opposed, Cornyn’s website put up a note saying they had received an unusually high volume of phone calls. Holler says Heritage Action had asked its members to call in, and the group takes at least partial credit for the senator’s phone troubles.

The group is directing all its might against the immigration bill. Their chances of success don’t look great. Comprehensive immigration reform has bipartisan support, and is one of the few issues that have brought together the Sierra Club and the Chamber of Commerce. K Street, as a general rule, loves it.

“This truly is a David versus Goliath,” Baird says. “We’ve been outspent on this a gazillion to one. This is why I caution people against saying ‘This is dead in the House, they won’t take it up after the farm bill.’ Too much money has been invested in this issue over the years, especially this year.”

“The capacity for House leadership to take on issues that divide the [conservative] movement is endless,” he adds. Heritage Action hopes to push those leaders rightward.

— Betsy Woodruff is a William F. Buckley Fellow at the National Review Institute.